You can create a .sublime-mousemap file for your plugin ([url=https://github.com/robcowie/SublimeTODO]SublimeTODO[\url] uses it). I don't know that there is a way to create a context, as with keymaps, so be careful not to override default functionality.

I really do appreciate the response; it's a little sad that that's so restricting though. Better not to use it at all, given its limitations. I guess just a keybinding around the cursor will be the way to go...